This invention relates generally to control devices as may be used in electrical switches or fluid valves or the like and in particular to thermal actuators, methods of controlling such of an expansible one of a pair of means for containing a vaporizable fluid in a thermal actuator, and actuating systems in which thermal actuators may be employed.
In the past, various thermal actuators and actuating systems utilizing such have been provided. Most of the past thermal actuators had a container or boiler adapted to be heated by various means well known in the art to vaporize at least a portion of a vaporizable liquid substantially completely filling the boiler, and the boiler was communicated through a relatively small opening with an expansible chamber also filled with the vaporizable liquid and having a wall free to move in response to changing pressures. When the boiler was heated under preselected conditions to effect vaporization of the liquid therein, the established vapors increased the pressure in the boiler forcing the liquid therefrom through the opening into the expansible chamber moving its movable wall for transmitting an actuating or output force to operate various electrical switch or fluid valve components. Of course, the boiler and expansible chamber were generally thermally insulated from each other thereby to effect cooling of the transferred liquid from the heated boiler to the relatively cooler environs of the expansible chamber, and upon termination of the heating of the boiler under other preselected conditions, the transferred liquid was returned upon contraction or collapse of the expansible chamber back to the boiler thereby to eliminate the output force transmitted by the movable wall of the expansible chamber.
One such past thermal actuator is shown in U.S. Pat. No. 2,595,846, and while this patented thermal actuator provided at least some advancement in the art, one of the disadvantageous or undesirable features thereof is believed to be that it was too fast acting in that only a relatively small amount of its vaporizable liquid was vaporized to effect the complete displacement of the liquid from the boiler to the expansible chamber. While the patented thermal actuator was effective to actuate the single switching device associated therewith, it is doubtful that other switching devices could be effectively combined therewith for sequential actuation by the patented thermal actuator due to the too fast or relatively uncontrolled actuation or liquid transfer characteristics thereof.
In U.S. Pat. No. 2,050,668, another thermal actuator is provided with a discharge nozzle which is beneath and angled with respect to the hot surface of the vaporizable liquid in the boiler thereby to cause a swirling action of the relatively cooler liquid returning to the boiler from the expansible chamber for effecting rather quick collapse thereof while obviating such collapse in the event of outside vibrations. The rate of collapse of the expansible chamber may be regulated by varying the angle of the discharge nozzle relative to the hot surface of the liquid in the boiler; however, it is believed that the disadvantageous or undesirable features discussed above with respect to U.S. Pat. No. 2,595,846, are also attendent to this patented device.
U.S. Pat. No. 2,086,819 discloses a thermal actuator having a valved passage through which a vaporizable liquid is passed in only one direction to an expansible chamber from a boiler upon heating to vaporize the vaporizable liquid therein. Another valved passage is provided through which the relatively cool liquid is returned in the other direction from the expansible chamber to the top portion of the boiler splashing it downwardly therein allegedly to increase the rate of cooling of the boiler and condensation therein upon termination of heating of the boiler. However, it is believed that the same disadvantageous or undesirable features discussed hereinabove with respect to the other prior art thermal actuators are also attendent to the thermal actuator of U.S. Pat. No. 2,086,819.
In U.S. Pat. No. 2,080,576, a diaphragm having an orifice therein is provided adjacent the bottom of a boiler which is communicated with an expansible chamber. Upon heating of the boiler, vapor is generated from a vaporizable liquid therein for depressing the liquid from the boiler through the orifice to the expansible chamber to effect the force transmitting actuation thereof. When heating of the boiler is terminated, the relatively cooler liquid returns from the expansible chamber in response to the collapse thereof through the orifice which creates a jet of the returning liquid so that is sprayed within the boiler allegedly causing quick cooling of the walls thereof. Nevertheless, it is believed that the thermal actuator of this patent also has the same disadvantageous or undesirable features as previously discussed herein with respect to the other prior art thermal actuators.